Eichhornia crassipes (water hyacinth) Native to South America Tristylous, clonal

1. Plant of the Day Eichhornia crassipes (water hyacinth) Native to South America Tristylous, clonal Invasive in Asia, Africa, North America, Australia Clogs waterways, blocks sunlight and reduces oxygen (Kills fish, increases mosquitoes) Zhang et al 2010 Uses: furniture, biofuel, bioremediation

2. “Any plant that crowds out cultivated plants” “A plant that grows where it is not wanted” “A plant out of place” What is a weed? “A plant is a weed if…its populations grow entirely or predominantly in situations markedly disturbed by man.” - HG Baker, 1965 weed = colonizer / ruderal

3. “Natural experiments” in plant evolution Colonization = opportunity for adaptation to novel environments

4. “Natural experiments” in plant evolution Agricultural weeds Derived from wild species / other crops • Adaptation to crop environment • Opportunities for repeated evolution of weedy forms • Gene flow / hybridization with progenitors

5. Colonizers Associated with Humans • Weedy: Human disturbance • Introduced: Human-assisted dispersal -introduced, alien, exotic, non-indigenous, or non-native species -about 1/4 of vascular plant species in Canada are introduced (1,229 species) • Invasive: Rapid spread and dominance -annual costs of invasive plants to the agricultural community are estimated at $2.2 billion (496 are invasive)

6. “Natural experiments” in plant evolution Introduced species Transferred outside range of natural dispersal • Founder effects? • Adaptation? > spread / invasion > range limits = NOT just colonizers of disturbed areas WEEDS

7. Founding events: Genetic variation lost Loss Gainin Variation (Multiple introductions) 25 20 Average = loss of 19% 15 # Species 10 5 0 -0.2 0.2 -1 1 2 3 Proportional Change of He in Introduced Populations [(introduced – source) / source]

8. Founding events • • Genetic bottlenecks probably common • • Non-random mating/asexual reproduction common • selfing • apomixis (asexual seeds) • vegetative spread • Genetic Drift

9. Founding events We know genetic bottlenecks can have fitness costs Decline in Hatching Success vs. Source Populations Number of Birds Introduced

10. Founding events Loss of Inbreeding depression in Hypericum canariense Hawaii San Diego, California 1 older cohorts Inbreeding depression for germination δ = outcross – self self 0.5 0 recent cohorts -0.5 -1 Invasion Core Leading Edge Invasion Core Leading Edge

11. Adaptation in Introduced Populations Depends on: Genetic variation Selection Extinction risk (population growth, r) New niche Introductions Niche axis 2 Niche axis 2 A B C D r > 0 r < 0 r << 0 Niche axis 1 Niche axis 1

12. Adaptation in Introduced Populations Simulation with demographic stochasticity Niche axis 2 A B C D Niche axis 1 Adaptation occurs ** NOT required for invasion Holt et al. 2005

13. Adaptation in Introduced Populations Simulation with demographic stochasticity Niche axis 2 A B C D Niche axis 1 Adaptation beneficial Produces invasion lag Holt et al. 2005

14. Adaptation in Introduced Populations Simulation with demographic stochasticity Niche axis 2 A B C D Niche axis 1 Adaptation required Produces invasion lag Holt et al. 2005

15. Adaptation in Introduced Populations Simulation with demographic stochasticity Niche axis 2 A B C D Niche axis 1 Adaptation too slow to prevent extinction **hard to study failed introductions Holt et al. 2005

16. Adaptation in Introduced Populations Punchline The relative difference in environments (niches) occupied by native and invading populations will dictate: • Extinction risk • Whether adaptation needed for establishment • Whether adaptation needed for invasion

17. Evolution and invasion What type of evolutionary changes occur during invasion? Could these changes contribute to “invasiveness”? Observation: many plant species grow larger and have greater reproduction and spread more rapidly in the invaded range compared to the native range (Crawley 1987). Why? Enemy release hypothesis Evolution of increased competitive ability Heterosis

18. Evolution and invasion 1. Plants trade off investment in self-defence for increased investment in growth and reproduction in the invasive range. 2. Plants trade off tolerance to abiotic stresses in native range for increased competitive and/or colonizing ability. 3. Invasive plants have greater vigor due to hybridization (e.g. heterosis, adaptive introgression, transgressive segregation).

19. Common Ragweed (Ambrosia artemisiifolia) Do invasive populations have higher growth and reproduction in benign environments compared to native populations? Is any advantage of the invasive populations lost in stressful conditions- i.e. is there evidence for a trade-off? Goal: compare growth rates, reproductive outputs, stress responses of native and invasive populations of ragweed in common gardens.

20. Common Ragweed (Ambrosia artemisiifolia) Wind pollinated, self incompatible monecious annual Problematic weed native to North America (sunflower, soybean, corn) Invasive in parts of Australia, Asia and Europe (e.g. 80% of arable land in Hungary is infested) Severely allergenic (hayfever, dermatitis)

21. Distribution of Ambrosia over the last 15 000 yrs Native to North America Common in the great plains for the past 15 000 yrs

22. Distribution of Ambrosia over the last 15 000 yrs Native to North America Common in the great plains for the past 15 000 yrs

23. Distribution of Ambrosia over the last 15 000 yrs Native to North America Common in the great plains for the past 15 000 yrs

24. Distribution of Ambrosia over the last 15 000 yrs Native to North America Common in the great plains for the past 15 000 yrs

25. Distribution of Ambrosia over the last 15 000 yrs Native to North America Common in the great plains for the past 15 000 yrs

26. Distribution of Ambrosia over the last 15 000 yrs Native to North America Common in the great plains for the past 15 000 yrs

27. Distribution of Ambrosia over the last 15 000 yrs Native to North America Common in the great plains for the past 15 000 yrs

28. Distribution of Ambrosia over the last 15 000 yrs Native to North America Common in the great plains for the past 15 000 yrs

29. Distribution of Ambrosia over the last 15 000 yrs Native to North America Common in the great plains for the past 15 000 yrs

30. Common garden experimental design 12 invasive, 22 native populations grown in UBC glasshouse • Experiment 1 - 1278 plants • 6.4 families/native population • 9.6 families/invasive population • Control, light, nutrient, herbivory stress • 3 blocks • Experiment 2 - 180 plants • 3.8 families/native population • 8.1 families/invasive population • Drought stress

31. Initial differences between the native and introduced range One week after transplant Two weeks after germination Invasive plants are larger than native plants

32. Biomass • There is a significant range*treatment interaction for biomass • Invasive plants tend to grow larger in the control and light stress • More equivalent growth in the nutrient stress

33. Reproductive success • The invasive plants flowered more frequently and had greater reproductive biomass in all treatments

34. Drought Experiment • Invasive plants wilted and died more quickly than native plants

35. More Evolutionary Trade-offs Evolutionary trade-off between drought tolerance and size also seen in yellow starthistle (Dlugosh et al. 2015)

36. Conclusions • Evolution can be very fast! • Biological invasions provide opportunities to study ‘evolution in action’! • Genetic bottlenecks are probably common, BUT: • Don’t last long (rapid population expansion) • Have weak effect on quantitative traits (many genes, many loci) • Rapid evolution is important for understanding ecology: • Adaptive evolution (usually) increases survival and reproduction – the same parameters that determine population growth. • Genetic constraints (e.g. trade-offs) limit the fitness benefits of adaptive evolution. Is this why species have range limits?